The present invention relates to a nacelle assembly and mounting assembly for a turbofan jet propulsion engine, and more particularly, to a nacelle assembly that is attached directly to the engine and to structure for shock mounting the entire engine and nacelle structure on an aircraft.
On some aircraft, jet propulsion engines are mounted adjacent the tail of the aircraft on each of the starboard and port sides of the fuselage. A variation of this configuration includes a third engine mounted in the tail of the aircraft with appropriate inlet ducting routed through the fuselage and having an inlet opening situated above the fuselage forwardly of the vertical stabilizer. These jet propulsion engines must be mounted on the aircraft by structure that can withstand the torque and axial loads generated by the engines and yet provide shock absorbing qualities to reduce or eliminate the vibrational energy transmitted from the engine through the mounting structure to the aircraft.
Two mounting arrangements have been used for mounting straight turbine type and low bypass turbofan jet propulsion engines of the prior art on aircraft. In one of the arrangements, shock absorbing mounting structure is attached directly to the turbine casing or to both the turbine and fan casing, as the case may be. In such a mounting arrangement, the nacelle structure is rigidly affixed to the shock mounting structure, necessitating the use of complex seals and complex vibration and shock mounting structure to allow for movement of the engine relative to the nacelle. In the other arrangement, the engine is shock mounted within a load bearing nacelle structure, which is in turn affixed to the aircraft fuselage, requiring a relatively strong but heavy nacelle structure.
With the advent of the high bypass turbofan engine, these prior art mounting techniques are undesirable for mounting the high bypass turbofan engines on an aircraft. For example, a stress bearing nacelle assembly must be constructed so that the entire nacelle can withstand and transmit the thrust and axial loads generated by the engine to the aircraft fuselage. Since large bypass turbofan engines require relatively large diameter nacelle structures, a significant weight penalty is incurred as the weight of an already relatively heavy stress bearing cowl increases with its size. Low bypass turbofan engines have in the past been directly shock mounted to fuselage structure by directly connecting the fan casing to a first mount and the turbine casing to a second mount.
The bleed air conduits and other accessory equipment normally exit from the top of the fan casing in a low bypass engine and for side fuselage mounted engines, must then extend peripherally or circumferentially around a portion of the fan casing and inwardly toward the fuselage through the mounting strut. With high bypass turbofan engines, this becomes impractical as routing the bleed air conduits and other accessories around the fan casing requires a substantial amount of diametral space and thus results in a large cowl cross section. Large diameter cowls are undesirable as the drag created by a cowl increases geometrically with its cross-sectional area. Moreover, such prior art nacelles have been constructed so that the the nacelle is rigidly affixed to the strut and/or to the fuselage. Such a mounting arrangement requires provision, then, for movement of the engine relative to the nacelle structure, increasing the complexity and weight of that structure.
Present day aircraft employing the foregoing engine configuration require separate and individually designed and constructed mounting structure and nacelle assemblies for each of the two or three engines, necessitating a significant initial investment in nacelle design and development. It is therefore desirable to design an engine and nacelle structure that can be interchanged among several engine mounting locations on a single aircraft without the necessity for substituting a large number of nacelle components.
It is therefore a broad object of the present invention to provide a structure for mounting and cowling a high bypass turbofan jet propulsion engine on an airplane, which structure can be employed to mount the engine on either side of the fuselage of an aircraft and also in the tail portion of an aircraft having a three engine configuration. Further objects of the present invention are to provide a light, strong, non-stress bearing nacelle assembly; to provide a nacelle assembly mounted directly on the engine that is free to move with the engine relative to the aircraft and the mounting structure; to provide a structure for shock mounting the engine and nacelle assembly to the aircraft; to provide a means for routing accessory bleed air and fuel conduits from the engine to the aircraft; to provide a versatile nacelle assembly and engine structure that can be interchangeably mounted on either the port or starboard sides of the fuselage of an aircraft or in the tail of an aircraft; to provide a relatively small diameter cowl for a high bypass turbofan engine; to provide a cowl structure with removable panels for easy access to the accessories for maintenance and repair; to provide fan air thrust reversing assemblies integrated into the cowl; to provide a nacelle assembly employing integrated turbine cowl, fan channel walls and exterior cowl members that can be easily opened and/or removed for direct access to the turbine core, including the burner assembly of the turbine; to provide an engine and a nacelle assembly that are integrated in design and structure and mutually supporting; to provide a nacelle assembly wherein all of the nacelle and engine components are mounted on the engine; to provide a shock mounting system for directly coupling a high bypass turbofan engine to a mounting strut or other aircraft structure; and to provide a mounting structure and nacelle assembly for a turbofan engine wherein vibration absorbing displacements occur between the engine/nacelle structure and airplane fixed structure.